This collaborative, multi-disciplinary project will exploit recent progress in genomics - the study of the complete genetic content of species and how it works - to greatly advance our knowledge of evolutionary relationships in the insect order Lepidoptera (moths and butterflies). A broad-scale "family tree" (phylogeny, genealogy) will be estimated using DNA sequences from approximately 250 species, representing all 126 families into which Lepidoptera are currently divided. A simultaneous review of known lepidopteran fossils will allow estimation of the geological ages of origin of the major groups. The 24 genes to be sequenced, identified by genome comparisons and screening in an earlier Tree of Life project, constitute far greater sampling of the genome than has heretofore been possible in most insects. Beyond providing a "backbone" phylogeny, the project is designed to catalyze a world-wide community effort to further resolve the lepidopteran tree, incorporating more traditional evidence from anatomy and behavior in addition to DNA. Annual lab workshops will help other lepidopterists to apply the numerous genes developed for this project, methods for which will be continuously updated on the web. An international network of >20 experts on Lepidoptera will help to choose species and provide specimens for project DNA sequencing. These experts will also jointly produce the first comprehensive catalog of anatomical features potentially informative about lepidopteran family genealogy, clarifying the chaotic terminology which has frustrated previous attempts to employ these traits for tree-building. A central project feature, also borrowed from modern genomics, will be an interactive website allowing the project team plus any other researcher to contribute and download data, methods, analysis and commentary on lepidopteran phylogeny at any level. The intent is to foster global cooperation and progress toward a fully-resolved tree. The web site will be "seeded" with most of the current evidence, to ensure a critical mass of information for others to build on. The same compilations will be used to greatly augment the available resources for public education on Lepidoptera, through contributions to popular web sites such as the Tree of Life.<br/><br/>The Lepidoptera are the largest single group of plant-feeding insects, numbering over 160,000 species. Ubiquitous and familiar, they are both a vital component of terrestrial ecosystems - what would birds and bats eat without them?- and arguably the most damaging group of pests overall to agriculture. As unusually conspicuous terrestrial non-vertebrates, Lepidoptera are extensively used in ecosystem assessment, and for educating and involving the public in environmental biology. They are also important focal organisms in many areas of biological research. For example, the evolutionary diversification of Lepidoptera in association with the rise of flowering plants, beginning in the Age of Dinosaurs, has figured prominently in the attempt to understand the origins of today's biodiversity. A well- corroborated "family tree" is essential both for understanding any aspect of lepidopteran evolution, and for constructing classifications that let us effectively organize and apply our voluminous knowledge about individual moth and butterfly species. However, relatively little progress toward such a tree has heretofore been made.